death in 20 years. our healthandscienceeditorjohn fowler tells us why it's an international first for an american and what it means for bay area residents. >> reporter: it happened somewhere in south contra costa county, where freeway overpasses offer ideal homes for colonies of mexican free tail bats. the species linked to this case of rabies. >> once the symptoms develop, it's universally fatal. >> after a bite or exposure to wild animal, the incubation phase is two to six months. >> reporter: health officials say the unidentified 34-year-old man was outside with friends who had found a bat, quote, flopping on the ground. one of them had the bat in a plastic bag. >> the gentleman who died of rabies went over and stuck his hand in the plastic bag and most likely was bitten. >> reporter: said to be a bay bridge contractor, he never reported the bite in march, took civilian work in iraq, and became infectious. the cdc says he flew home to contra costa county june 14th. four days later, san francisco to bangkok for two weeks vacation, had close contact with two people, flew back to